Special Expert Witnesses and the Jurisdiction of a Single Judge in Criminal Proceedings
Legal Analysis on Special Expert Witnesses and the Jurisdiction of a Single Judge in Criminal Proceedings
A special expert is, in substance, a form of expert witness called to assist the court in matters requiring specialized knowledge beyond ordinary judicial understanding. Where the prosecution relies on such a person merely as a witness to provide professional explanation or expert opinion at trial, the opposing party is not required to be given advance notice of the expert’s statement three days prior to testimony. The reason is that this is not a case in which the court itself has ordered the special expert to conduct an examination and submit a written opinion or report under Section 243, paragraph 2 of the Thai Criminal Procedure Code. The statutory requirement concerning prior disclosure applies specifically to a court-appointed expert report of that nature, not to every instance in which a party calls an expert to testify. Accordingly, when the expert is produced by the prosecution as part of its evidentiary case, the testimony is treated as ordinary expert evidence, and no such three-day prior notification is legally necessary. This principle is reflected in Supreme Court precedent, including Dika No. 444/2510.
In a separate issue, where a judge of a Provincial Court sits alone and hears a criminal case involving the offenses of forgery of documents and assault causing bodily harm, each offense carrying a maximum statutory punishment within the jurisdictional competence of a single judge, the proceedings are lawful even if, upon conviction on both counts, the total punishment imposed becomes greater when taken together. The legality of the composition of the court is determined by considering the maximum penalty prescribed for each individual count separately, not by aggregating the potential or actual punishment across multiple counts. Therefore, if each charge independently falls within the authority of a single judge, that judge may lawfully conduct the trial and render judgment alone. The subsequent fact that the accused is convicted on both counts and receives a combined sentence does not retroactively deprive the judge of jurisdiction. This approach is consistent with Supreme Court precedents such as Dika Nos. 530/2480 and 1356–1521/2501.
Furthermore, where the court orders the defendant to be detained as a habitual offender for a specified period, such order is likewise lawful. The legal basis is that detention in this context is not regarded as a punishment, but rather as a protective or preventive measure imposed under the law upon a habitual offender. For that reason, the power of a single judge is not defeated merely because such detention is added to the sentence. This principle has also been affirmed by the Supreme Court in Dika No. 24/2513.
In conclusion, the special expert in the first issue is properly classified as an expert witness, and no three-day advance notice is required unless the case falls within the specific statutory mechanism of a court-ordered expert report under Section 243, paragraph 2. In the second issue, the judgment rendered by a single Provincial Court judge is lawful both in respect of jurisdiction over the offenses and in respect of the order of detention imposed upon the defendant as a habitual offender